/Engine/Plugins/Editor/UVEditor/Source/UVEditorTools/Public/Selection/UVToolSelectionAPI.h
Broadcasted right before a selection change is applied (and therefore before a selection change transaction is emitted). Useful if a user wants to emit their own bookend transaction first.
typedef TMulticastDelegate_TwoParams< void, bool bEmitChangeAllowed, uint32 SelectionChangeType > FOnPreSelectionChange